System and method for improved vehicle response during vehicle acceleration conditions

ABSTRACT

A vehicle control method for a vehicle having an internal combustion engine coupled to a torque converter is described. In one embodiment, the engine air flow and spark are adjusted to control torque converter operation. The method can improve vehicle response to driver accelerator commands.

FIELD

The present application relates to engine and vehicle control, and inone example relates to operation during vehicle acceleration followingdeceleration.

BACKGROUND AND SUMMARY

Internal combustion engines are controlled in many different ways toprovide acceptable driving comfort during all operating conditions. Somemethods use engine output, or torque, control where the actual enginetorque is controlled to a desired engine torque through an outputadjusting device, such as with an electronic throttle, ignition timing,or various other devices.

Under some conditions, there is the potential for poor driveability whenthe vehicle operator releases and subsequently engages the acceleratorpedal. Specifically, as described in U.S. Pat. No. 6,266,597,transmission or driveline gear lash crossing during such conditions candegrade driver feel. For example, when the engine transitions fromexerting a positive torque to exerting a negative torque (or beingdriven), the gears in the transmission or driveline separate at the zerotorque transition point. Then, after passing through the zero torquepoint, the gears again make contact to transfer torque. This series ofevents produces an impact, which if transmitted to the driver is calledclunk, resulting in poor driveability and customer dissatisfaction.

This disadvantage of the prior art is exacerbated when the operatorreturns the accelerator pedal to a depressed position, indicating adesire for increased engine torque. In this situation, the zero torquetransition point must again be traversed. However, in this situation,the engine is producing a larger amount of torque than duringdeceleration because the driver is requesting acceleration. Thus,another, more severe, impact is generally experienced due to thetransmission or driveline lash during the zero torque transition.

As such, in U.S. Pat. No. 6,910,990, the system controls engine torqueto transition through the transmission or driveline lash zone bylimiting a rate of torque increase during such conditions. In otherwords, when near the transmission lash zone, engine torque is adjustedat a predetermined rate until the system passes through the transmissionlash zone. Further, the limiting may be adjustable based on operatingconditions. By varying the limitation on the torque change in this way,driveability can be improved.

However, the inventors herein have recognized a disadvantage with suchan approach. In particular, while rate limiting torque changes mayreduce clunk, it may also increase a response delay to the pointnoticeable by the driver. Further, the greater the reduction in clunk(i.e., the more torque increases or decreases are limited), the greaterthe response delay.

The above disadvantages may be overcome by a vehicle control method fora vehicle having an internal combustion engine coupled to atransmission, the transmission coupled to wheels on a road. Thistransmission may be an automatic transmission with a torque converterwith a torque converter bypass clutch, the torque converter having aninput speed and an output speed, the torque converter coupled to agearbox. This automatic transmission converter bypass clutch may be atminimal capacity (“open converter”), being modulated to maintain atargeted level of clutch slip or capacity or it may be at full capacity(“hard locked”). The method comprising of in response to a drivertip-out during at least some conditions, decreasing powertrain output sothat positive torque is not transmitted to the wheels, and after saidtip-out and in response to a driver tip-in, and at least duringtransitioning to transmission of positive powertrain torque to thewheels, retarding ignition timing while adjusting engine airflow untildriveline torque has transitioned to the positive side of lash, and thenadvancing spark angle to rapidly provide output torque.

In this way, it may be possible to coordinate multiple torque actuatorsduring a driver tip-in to both reduce clunk without substantiallyincreasing total response time. For example, by coordinating throttleand ignition timing adjustments during a driver tip-in in this way, itis possible to, in effect, increase pre-charging of the intake manifoldand cylinders with airflow so that once the transition through the lashzone is complete, a more rapid torque increase is possible.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram of a vehicle illustrating various powertraincomponents;

FIG. 2 is a block diagram of an engine;

FIG. 3 is a high level flowchart of a routine for controlling the engineand powertrain;

FIG. 4 is a graph illustrating example operation;

FIG. 5 is a state diagram of example control logic and routines; . . .

FIG. 6 is a timing diagram showing example operation according to FIG.5; and

FIG. 7 is a graph illustrating additional example operation.

DETAILED DESCRIPTION

Referring to FIG. 1, internal combustion engine 10, further describedherein with particular reference to FIG. 2, is shown coupled to torqueconverter 11 via crankshaft 13. Torque converter 11 is also coupled totransmission 15 via turbine shaft 17. Torque converter 11 has a bypassclutch (not shown) which can be engaged, disengaged, or partiallyengaged. When the clutch is either disengaged or being disengaged, thetorque converter is said to be in an unlocked state. Turbine shaft 17 isalso known as transmission input shaft. In one embodiment, transmission15 comprises an electronically controlled transmission with a pluralityof selectable discrete gear ratios. Transmission 15 may also comprisesvarious other gears, such as, for example, a final drive ratio (notshown). Alternatively, transmission 15 may be a continuously variabletransmission (CVT).

Transmission 15 may further be coupled to tire 19 via axle 21. Tire 19interfaces the vehicle (not shown) to the road 23. Note that in oneexample embodiment, this powertrain is coupled in a passenger vehiclethat travels on the road.

Internal combustion engine 10 comprising a plurality of cylinders, onecylinder of which is shown in FIG. 2, is controlled by electronic enginecontroller 12. Engine 10 includes combustion chamber 30 and cylinderwalls 32 with piston 36 positioned therein and connected to crankshaft13. Combustion chamber 30 communicates with intake manifold 44 andexhaust manifold 48 via respective intake valve 52 and exhaust valve 54.Exhaust gas oxygen sensor 16 is coupled to exhaust manifold 48 of engine10 upstream of catalytic converter 20.

Intake manifold 44 communicates with throttle body 64 via throttle plate66. Throttle plate 66 is controlled by electric motor 67, which receivesa signal from ETC driver 69. ETC driver 69 receives control signal (DC)from controller 12. Intake manifold 44 is also shown having fuelinjector 68 coupled thereto for delivering fuel in proportion to thepulse width of signal (fpw) from controller 12. Fuel is delivered tofuel injector 68 by a conventional fuel system (not shown) including afuel tank, fuel pump, and fuel rail (not shown).

Engine 10 further includes conventional distributorless ignition system88 to provide ignition spark to combustion chamber 30 via spark plug 92in response to controller 12. In the embodiment described herein,controller 12 is a conventional microcomputer including: microprocessorunit 102, input/output ports 104, electronic memory chip 106, which isan electronically programmable memory in this particular example, randomaccess memory 108, and a conventional data bus.

Controller 12 receives various signals from sensors coupled to engine10, in addition to those signals previously discussed, including:measurements of inducted mass air flow (MAF) from mass air flow sensor110 coupled to throttle body 64; engine coolant temperature (ECT) fromtemperature sensor 112 coupled to cooling jacket 114; a measurement ofthrottle position (TP) from throttle position sensor 117 coupled tothrottle plate 66; a measurement of turbine speed (Wt) from turbinespeed sensor 119, where turbine speed measures the speed of shaft 17,and a profile ignition pickup signal (PIP) from Hall effect sensor 118coupled to crankshaft 13 indicating an engine speed (N). Alternatively,turbine speed may be determined from vehicle speed and gear ratio.

Continuing with FIG. 2, accelerator pedal 130 is shown communicatingwith the driver's foot 132. Accelerator pedal position (PP) is measuredby pedal position sensor 134 and sent to controller 12.

In an alternative embodiment, where an electronically controlledthrottle is not used, an air bypass valve (not shown) can be installedto allow a controlled amount of air to bypass throttle plate 62. In thisalternative embodiment, the air bypass valve (not shown) receives acontrol signal (not shown) from controller 12.

As described above, the present application is directed, in one example,to solving disadvantages that occur when the driver “tips-in” (appliesthe accelerator pedal) after the torque in the driveline hastransitioned into the negative region. In such cases, the drivelineelements will have to transition through their lash region to providepositive torque to the wheels, where the transition through the lashregion can produce an objectionable “clunk” if the impact velocity ofthe driveline elements is too fast.

In an automatic transmission vehicle, to have positive torque producedby the torque converter and transmitted to the driveline, the enginespeed must be above turbine speed and the turbine speed must be at thesynchronous turbine speed or the converter bypass clutch must have somecapacity to transmit torque and the engine torque is positive and theslip across the clutch is non-negative. (The torque converter slip(engine speed—turbine speed) is greater than 0 when positive torque isbeing delivered). If the transition from negative to positive converterslip and/or torque is not properly managed, then the engine canaccelerate too fast through this region (beginning to produce positivetorque) or the converter clutch torque can rise too fast resulting in ahigher rise rate of output shaft torque accelerating the elements in thedriveline. Higher torque levels before the lash in the driveline beingtaken up can then produce higher impact velocities and make “clunk” morelikely. To a first approximation for an “open” converter, the rise rateof torque in the driveline (non-shifting) may be proportional to therate of engine acceleration when the engine speed>synchronous turbinespeed.

Under some conditions, the engine should be controlled so that theengine torque and/or acceleration is reduced sufficiently while thedriveline elements are accelerating to produce positive drivelinetorque, but the engine torque/acceleration and driveline torque shouldalso be responsive to the driver's demand before and after thistransition so that the driver perception of any lag in the engineresponse is reduced.

While an engine torque estimation model in the controller can be used,errors in the estimation can reduce estimate accuracy and thus theprecision to indicate whether the driveline torque is slightly positiveor slightly negative. As such, in one embodiment that can be used aloneor in addition to a torque estimate, additional measurements, such astorque converter input and output speeds can be used to accuratelyindicate when the vehicle is beginning and ending transitioning throughthe lash region, even in the presence of external noise factors.

Specifically, in one example for a torque converter equipped vehicle, atip-in management and control routine can be used to adjust enginetorque control to control engine acceleration just as the engine speedis exceeding turbine speed. Further, the engine torque may be controlledvia multiple actuators, such as using slower throttle control and fasterignition timing control in a coordinated way to minimize any driverperception of rate limited torque during the transition through the lashregion. For example, various example engine control strategies usingcoordinated throttle and spark control to manage the transition fromnegative driveline torque to positive driveline torque through drivelinelash with improved robustness and responsiveness is described below withregard to FIGS. 3-7. Because of the coordinated use of throttle andspark and the triggering of control system actions based on measuredspeeds across a torque converter, the operation of this system canprovide various advantages as noted herein.

Referring now to FIG. 3, a routine is described for controlling engineand vehicle operation during a driver tip-in where the transitionthrough a gear lash zone for an open converter configuration is managedwhile still providing acceptable increasing torque response. In 310, theroutine determines whether a previous driver tip-out has been detectedand the torque converter is unlocked, or partially un-locked. In oneexample, the routine determines whether the driver is depressing theaccelerator pedal by determining whether the pedal position is less thanthe preselected value. Note that this preselected value can be anadaptive parameter that tracks variations in the closed pedal positiondue to sensor aging, mechanical wear, and various other factors. Alsonote that in response to a driver tip-out being detected, powertrainoutput may be decreased so that positive torque is not transmitted tothe wheels, for example, the wheels may be driving the engine throughthe transmission and/or torque converter. Further, during some tip-outconditions, fuel injectors may be deactivated to further reduce enginetorque (or increase engine braking), possibly improving fuel economy.However, may be considered in some examples when transitioning throughthe lash zone, for example.

When the answer to 310 is YES, the routine continues to 312. In 312, theroutine determines whether a substantial driver tip-in has beendetected. Again, this may be determined based on pedal position, or thecorresponding increase in desired torque caused by depression of thedriver pedal, for example. If so, the routine continues to 316.

In 314, the routines whether the powertrain is in or near a gear lashzone. For example, the routine may utilize the torque converter inputand output speeds to determined whether the speeds are within a selectedrange of equal speeds, for example, and whether the speeds are greaterthan a synchronous speed, for example. If not, the routine continues to318 where a requested torque increase may be provided by a throttleincrease and an advance of ignition timing (if the current timing isretarded from a maximum torque timing, for example).

Otherwise, if the answer is YES to 314, the routine continues to 316 todetermine whether torque increase rate limiting is selected based onoperating conditions. For example, the routine may determine whether tolimit a rate of torque increase during the lash zone to reduce apotential impact caused by such lash as noted herein. If so, the routinecontinues to 320 to limit torque increase by retarding ignition timingwhile still increasing airflow by increasing the throttle angle, forexample. In this way, it is possible to limit torque increase duringtransitions through the lash zone via spark retard, yet by continuing anincrease in airflow without the limitation such as in prior approaches,the torque can be even more rapidly increases once through the lashzone. Such operation is illustrated in more detail in the propheticexample of FIG. 4.

Specifically, FIG. 4 shows an example response to a driver tip-in wherethe powertrain output torque transitions from negative to positive, asshown by the top graph. The lash zone, or approximately zero torquetransmission location is illustrated with the dashed horizontal line,where the lower dotted line indicates an example speed ratio threshold(e.g., torque converter input speed is 0.95 of torque converter outputspeed) and the upper dotted line indicates an example speed ratiothreshold (e.g., torque converter input speed is 1.05 of torqueconverter output speed). Below the powertrain output torque the graphillustrates driver pedal position (APP) and then throttle position (TP)of an electronically controlled throttle plate. Below throttle positionthe graph illustrates ignition timing, and specifically timing relativeto a maximum torque timing (mbt), where spark timing below the mbt linerepresents retard from mbt. Finally, the bottom illustration shows theairflow response.

FIG. 4 shows three example response, with the first (A) illustrating atip-in with no mitigation in ignition timing or airflow, and thus themost likely to cause objectionable clunk; the second (B) illustrating atip-in with a limitation of engine torque via the throttle, or airflow,which may be used to reduce the effect of clunk; and the third (C)illustrating compensation via coordination of throttle and spark inaccordance with FIG. 3.

In the first response (A), neither engine torque, nor throttle, norspark, are used to rate-limit the powertrain output during thetransition through the lash zone. Thus, clunk may be experienced undersome conditions, however a quick response is experience by the driver.

In the second response (B), throttle position is used to rate limittorque increase during the transition. Once through the lash zone, thethrottle can then continue to increase unrestricted to deliver thedriver requested torque. However, while the limiting may reduce clunk,driver response may be reduced by the delay in delivering airflow, dueto the combination of manifold dynamics, throttle dynamics, and the ratelimiting. In other words, as shown by Figure, the torque response in Bis permanently delayed from A.

In the third response (C), coordination of throttle position and sparkretard are used to transition through the lash zone, while stillproviding acceptable response. As shown by FIG. 4, while there is aperiod of delay in response when transitioning through the lash zone,the torque response of C is able to “catch up” to the torque response ofA. By using spark retard during the transition, while allowing airflowto continue to rise substantially un-restricted, it is possible to bothreduce clunk, and maintain driver performance over a longer scale.

Returning to 320, the level to which engine torque can be managed orreduced relative to requested output may be dependent on operatingconditions, in one embodiment. For example, an allowable rate ofincrease in engine torque may be based on various factors, such as basedon information that relates to status and conditions of the engine andvehicle indicative of whether and to what extent clunk can affect drivefeel, and the extent rate limiting requested engine torque may reducevehicle response. In particular, in one example, the routine utilizesthe sensed accelerator pedal position (PP), the torque converter speedratio, the vehicle speed, and the ratio of vehicle speed to enginespeed. In one example, the allowable rate of increase may be determinedas a four dimensional function of the pedal position, speed ratio,vehicle speed, and engine speed to vehicle speed ratio.

Concluding the discussion of FIG. 3, if the answer to 314 or 316 is no,the routine continues to 318 in this example.

Referring now to FIG. 5, an alternative embodiment illustrated via astate diagram is shown. Specifically, each block shows a control logicstate, with transitions amount the states shown by lines, where thedirection of the transition is indicated with an arrow. Further theblocks indicate their state value (e.g., block 510 is STATE 0, asindicated by the mode parameter tq_tim_mode). Further, each blockindicates potential states to which the control may transition via thenumbers in parenthesis.

Block 510 shows STATE 0, in which control logic for making engineadjustments for transitioning through the lash zone in response to atip-in are not activated. Specifically, the logic is disarmed, and thesystem is at part pedal (e.g., the driver is partly tipped in) waitingfor a tip-out. Further, there is currently no adjustment to enginethrottle angle or ignition timing (SAI). As indicated in theparenthesis, from block 410, the control may transition to either STATE1, or stay in STATE 0.

512 shows a transition from STATE 0 to STATE 1, which may be based onseveral alternative conditions. A first transition condition is based ontorque converter slip, in either an overrunning or non-overrunningcondition. Specifically, if negative slip and a low torque request(i.e., less than a threshold value TQ_ARM) are detected, the statetransitions. A second transition condition is independent of slip, butrather based on a low actual torque (i.e., less than a threshold valueTQ_ARM) being detected.

514 shows a transition from STATE 1 to STATE 0, which may occur based onslip for either an overrunning or non-overrunning condition in which theroutine identifies whether the powertrain has reached a positive slipvalue (e.g., torque converter input speed greater than torque converteroutput speed, or whether the transmission is in neutral or disabled.Alternatively, the transition may occur independent of slip based onwhether the powertrain has reached a positive actual torque (i.e.,greater than a threshold value TQ_DISARM).

Block 516 shows STATE 1, in which control logic prepares for a tip-in.In this case, the control logic for making adjustments during atransition to a driver tip-in through the lash zone is armed, and theroutine is waiting for a tip-in to occur. Further, there is currently noadditional lash-based adjustment to engine throttle angle or ignitiontiming (SAI) in this state. As indicated in the parenthesis, from block516, the control may transition to either STATES 3, 2, or 0. While inSTATE 1, the vehicle powertrain torque levels at the driver axle are lowor negative, depending on operating conditions.

518 shows a transition from STATE 1 to STATE 2 based on whether asignificant positive torque request (i.e., desired torque increases pasta threshold level) is detected. Further, 520 shows a transition fromSTATE 1 to STATE 0 based on whether a torque request has dropped (i.e.,below a lower threshold) and is below a torque control level. 522 showsa transition from STATE 1 to STATE 3 which may be based on slip ineither an overrunning or non-overrunning condition, such as based onwhether the torque converter speed ratios have entered a range of lashvalues, such as between 0.95 and 1.05. In this case, the system can bedetermined to have begun a transition through lash region based on slip.Alternatively, the transition may be independent of slip, such as basedon whether actual torque becomes greater than a threshold.

Block 524 shows STATE 2, in which control logic increases engine torque.In this case, the control logic detects a positive torque request thatmay produce clunk, and calculates a limited airflow increase as the lashregion is approached. Specifically, a throttle position of theelectronically controlled throttle is clipped. As indicated in theparenthesis, from block 524, the control may transition to either STATES4, 3, 1, or 0.

526 shows a transition from STATE 2 to STATE 3 which may be non-slipbased via a exceeding a timer. Alternatively, the transition may be slipbased in either an overrunning or non-overrunning condition based onwhether the powertrain has begun to transition through lash region basedon torque converter speeds, e.g., has the ratio of torque converterinput speed to torque converter output speed risen above a thresholdvalue (e.g., 0.95). Still further, the transition can be non-slip based,such as whether the powertrain has begun to transition through the lashregion based on actual engine torque.

528 shows a transition from STATE 2 to STATE 4 which may be based ontorque converter slip values and a timer value (e.g., exceeding athreshold time in STATE 2). Further, 530 shows a transition from STATE 2to STATE 4 which also may be based on torque converter slip values and atimer value (e.g., exceeding a threshold time in STATE 2).

Block 532 shows STATE 3, in which control logic holds or rate-limitsengine and/or powertrain torque. In this case, the control logic adjustsspark timing (e.g., ignition timing retard from maximum torque timing)and optionally throttle position to clip engine torque and/oracceleration using a torque rate limit to reduce clunk through the lashzone. As indicated in the parenthesis, from block 532, the control maytransition to either STATES 4, or 0. For a torque converter where theconverter clutch capacity is small enough to allow enough slip such thatengine acceleration is clearly related to engine torque and converterhydraulic torque as the dominant dynamics (instead of converter clutchtorque), this clipping, holding or rate-limiting of can be conditionalbased on engine acceleration or slip feedback.

534 shows a transition from STATE 3 to STATE 4, which may be based onslip in either an overrunning or non-overrunning condition, such asbased on whether the torque converter speed ratios have exited a rangeof lash values, such as between 0.95 and 1.05 (i.e., whether thepowertrain has completed a transition through the lash region based ontorque converter speeds, e.g., has the ratio of torque converter inputspeed to torque converter output speed risen above a threshold value,such as 1.05). The transition may also be triggered independent of slip,and the determination of completing the transition may be based onwhether actual torque is greater than a threshold value. Still further,the transition may be triggered by whether a downshift of thetransmission gears in progress, or whether a timer value has been exceedfor a threshold time in STATE 3.

536 shows a transition from STATE 3 to STATE 0 based on whether a torquerequest returned to a lower torque value and the pedal is a closedposition before a transition through the lash zone is completed, or thetransmission is in neutral or disabled. Any of these conditions willthus cause the routine to transition to STATE 0.

Block 538 shows STATE 4, in which control logic ramps in torqueincreases after completing a transition through the lash zone.Specifically, the limits on spark timing and throttle (if any) areramped out to make the torque output available to provide the desireddriver response. This can be done rapidly or more smoothly, depending onoperating conditions, for example. As indicated in the parenthesis, fromblock 538, the control may transition to STATE 0.

540 shows the only transition from STATE 4, specifically, a transitionfrom STATE 4 to STATE 0. The transition of 540 may be triggered when theramping of throttle and spark timing is completed (e.g., when ignitiontiming retard has ramped out), or when a timer for being in STATE 4 hasexceeded a threshold.

As previously noted above, the transition diagram of FIG. 5 illustratesan example routine that may be used to control operation through thelash zone to both reduce clunk while still providing a rapid driverresponse. Further, in this example, both slip based and non-slip basedconditions may be used to achieve robust operation over a variety ofoperation conditions, such as either a locked or unlocked torqueconverter, manual transmissions, etc.

Further, in one or more of the above states (and in one embodiment inall states), the airflow control and/or the spark control can be subjectto overrides based on driver input (pedal position, rate, or somecombination) so that as the driver demand increases the systemresponsiveness can also increase. Further, in one, some, or all states,the torque, airflow and spark limiting can be subject to overrides basedon commanded transmission downshifts and downshifts that are ‘inprogress’ (ratio is changing) to bring engine torque up quickly toenable the transmission to make a smooth and responsive shift. Forexample, torque, airflow and spark limiting can be subject to overridesin all states if a downshift commanded based on driver demand isdetected. Finally, transitions between modes, or the timing or use ofsome limiting states are responsive to driver demand downshifts inprogress (transmission ratio starting to change).

Referring now to FIG. 6, it shows a timing diagram corresponding to theoperation of FIG. 5. Specifically, it shows the response to a drivertip-in during various STATES, or modes, and illustrates adjustments toboth throttle position and ignition timing. In the graph, the followinglabels are used: L2 is the initial mode 2 torque command level forthrottle and spark, L3 is the initial mode 3 torque command level forspark, R2 is the rate of increase in the throttle and spark torquecommands during mode 2, R3 a is the rate of increase in the throttlecommand during mode 3 (note that the throttle command does not step downlike the spark command, R3 b is the rate of increase for spark in mode3, and R4 a and R4 b are similar to R3 a and R3 b. The graph alsoillustrates the airflow holding timer (tq_desem_hld_tmr) which counts upduring time TM5, and the torque multiplier (tq_desam_mul) which countsdown during time TM6. Finally, it shows the enable flag (tq_desem_ena)indicating that the above control logic is active.

Referring now to FIG. 7, another example of system operation isillustrated in which coordinated throttle and spark adjustments areprovided to manage driveline lash transition. Specifically, the plotshows the coordinated way that engine airflow is used to accelerate theengine up to turbine speed at maximum spark, then spark is retarded toslow engine acceleration through the driveline lash zone and then torqueis again increased rapidly via spark and airflow after lash has beencrossed.

The top graph of FIG. 7 shows turbine speed (torque converter outputspeed) in solid, and engine speed (torque converter input speed) indashed. Further, the bottom graph shows engine airflow in solid andabsolute spark advance in dashed. The x-axis of both graphs shows timein seconds. While this example is based on vehicle data, it representsonly one example transition, and as noted herein, various alternativesare possible.

During the initial vehicle operation (around 710), the fuel injectorsare cut-out (e.g., deactivated). While in this particular example thesystem incorporates injector cut-out during deceleration or drivertip-out conditions, injector cut-out may also be eliminated. Further,during the initial operation, the torque converter slip (turbinespeed—engine speed) is controlled to approximately −50 rpm, e.g., via alock-up clutch, number of cylinders active, etc. Then, around 712,engine airflow is increased, injectors are activated, and the sparkangle is maintained at approximately mbt, in response to a drivertip-in. Then, around 714, a small slip across the torque converter ismaintained until the lash zone is crossed via airflow and spark retardcontrol. Around 716, airflow is further increased for good torqueresponse, with spark retarded as need to hold engine speed through thelash zone and then increase torque quickly. Finally, around 718, thetransmission control (e.g., clutch duty cycle) allows the converter toslip as engine torque is increased.

As will be appreciated by one of ordinary skill in the art, the specificroutines and block diagrams described below in the flowcharts mayrepresent one or more of any number of processing strategies such asevent-driven, interrupt-driven, multi-tasking, multi-threading, and thelike. As such, various steps or functions illustrated may be performedin the sequence illustrated, in parallel, or in some cases omitted.Likewise, the order of processing is not necessarily required to achievethe features and advantages of the disclosure, but is provided for easeof illustration and description. Although not explicitly illustrated,one of ordinary skill in the art will recognize that one or more of theillustrated steps or functions may be repeatedly performed depending onthe particular strategy being used. Further, these Figures graphicallyrepresent code to be programmed into the computer readable storagemedium in controller 12.

It will be appreciated that the configurations and embodiments disclosedherein are exemplary in nature, and that these specific embodiments arenot to be considered in a limiting sense, because numerous variationsare possible. For example, the above valve can be applied in a varietyof areas, including various types of engines, such as V-6, 1-4, 1-6,V-12, opposed 4, and other engine types.

The subject matter of the present disclosure includes all novel andnonobvious combinations and subcombinations of the various systems andconfigurations, and other features, functions, and/or propertiesdisclosed herein.

The following claims particularly point out certain combinations andsubcombinations regarded as novel and nonobvious. These claims may referto “an” element or “a first” element or the equivalent thereof. Suchclaims should be understood to include incorporation of one or more suchelements, neither requiring nor excluding two or more such elements.Other combinations and subcombinations of the disclosed features,functions, elements, and/or properties may be claimed through amendmentof the present claims or through presentation of new claims in this or arelated application. Such claims, whether broader, narrower, equal, ordifferent in scope to the original claims, also are regarded as includedwithin the subject matter of the present disclosure.

1. A vehicle control method for a vehicle having an internal combustionengine coupled to a torque converter, the torque converter having aninput speed and an output speed, the torque converter coupled to atransmission, the transmission coupled to wheels on a road, the methodcomprising: in response to a driver tip-out, decreasing powertrainoutput so that positive torque is not transmitted to the wheels; andafter said tip-out and in response to a driver tip-in under a firstoperating condition, increasing engine airflow while performing ignitiontiming more advanced than a first ignition timing to increase torqueconverter input speed toward torque converter output speed; furtherincreasing engine airflow while performing ignition timing more retardedthan said first ignition timing to limit a torque increase during atransition from torque converter input speed less than torque converteroutput speed to torque converter input speed greater than torqueconverter output speed; and then further increasing engine airflow whileperforming ignition timing more advanced than said first ignition timingto provide a torque output increase.
 2. The method of claim 1 furthercomprising: after said tip-out and in response to said driver tip-inunder a second operating condition, increasing engine airflow whileperforming ignition timing more advanced than said first ignition timingto increase torque converter input speed toward and above torqueconverter output speed.
 3. The method of claim 2 wherein in response tosaid tip-out, at least one fuel injector is deactivated.
 4. The methodof claim 3 wherein said ignition timing is retarded from said firsttiming until torque converter input speed is greater than torqueconverter output speed plus a threshold.
 5. The method of claim 4wherein said threshold varies with operating conditions, and wheredecreasing powertrain output so that positive torque is not transmittedto the wheels includes transitioning from torque converter output speedgreater than torque converter input speed to torque converter outputspeed less than torque converter input speed, the torque converter beingunlocked during the transitioning.
 6. The method of claim 1 wherein alimit of said torque increase varies with operating conditions.
 7. Avehicle control method for a vehicle having an internal combustionengine coupled to a torque converter, the torque converter having aninput speed and an output speed, the torque converter coupled to atransmission, the transmission coupled to wheels on a road, the methodcomprising: in response to a driver tip-out, decreasing powertrainoutput so that positive torque is not transmitted to the wheels; andafter said tip-out and in response to a driver tip-in under a firstoperating condition, increasing engine airflow while performing ignitiontiming more advanced than a first ignition timing to increase torqueconverter input speed toward torque converter output speed; furtherincreasing engine airflow while performing ignition timing more retardedthan said first ignition timing to limit a torque increase during atransition from torque converter input speed less than torque converteroutput speed to torque converter input speed greater than torqueconverter output speed; and then further increasing engine airflow whileperforming ignition timing more advanced than said first ignition timingto provide a torque output increase, the engine airflow continuallyincreasing from torque converter input speed being less than torqueconverter output speed to torque converter input speed being greaterthan torque converter output speed.